Miniature fluid-cooled heat sink with integral heater

ABSTRACT

A temperature control device that includes a miniature liquid-cooled heat sink with integral heater and sensing elements is used as part of a system to provide a controlled temperature surface to an electronic device, such as a semiconductor device, during the testing phase. The temperature control device includes an interface surface configured to provide a thermal path from the device to a device under test. One such device has a liquid-cooled heat sink comprising a first heat transfer portion in a first plane and a second heat transfer portion in a second plane. The first and second heat transfer portions establish a three-dimensional cross-flow of coolant within the heat sink structure. An alternate embodiment includes parallel fluid conduits, each having a three-dimensional microchannel structure that directs coolant flow in three dimensions within the fluid conduits. Coolant flows in opposite directions through adjacent fluid conduits, thus resulting in a three-dimensional cross-flow within the heat sink structure.

FIELD OF THE INVENTION

The present invention relates generally to a temperature control devicethat controls the temperature of an electronic device during testing.More particularly, the present invention relates to a miniatureliquid-cooled heat sink with integral heater and sensing elements formaintaining constant operating temperature of the electronic deviceunder test.

BACKGROUND OF THE INVENTION

Electronic devices, such as integrated circuit chips, are usually testedprior to use. Device manufacturers typically perform a number ofelectrical and physical tests to ensure that the devices are free fromdefects and that the devices function according to their specifications.Common types of device testing include burn-in testing and electricalperformance testing.

The operating temperature of an electronic device under test (“DUT”) isan important test parameter that usually requires careful monitoringand/or regulating. For example, an electrical test procedure maydesignate a number of specific test temperatures or a specific range oftest temperatures. Consequently, the prior art is replete with differenttypes of temperature control systems, heat sink components, and heaterelements designed to heat, cool, and otherwise control the operatingtemperature of a DUT. These temperature control systems are designed tomaintain a steady state DUT operating temperature during the electronictesting procedure. However, it can be difficult to regulate thetemperature of a DUT if the DUT exhibits rapid or excessive internaltemperature changes while being tested; the electronic devices withinthe DUT often generate heat which causes such internal temperaturechanges. The prior art configurations may not be capable of efficientlyand effectively compensating for rapid temperature fluctuationsgenerated by the DUT.

BRIEF SUMMARY OF THE INVENTION

A preferred embodiment of the present invention is realized as atemperature control device that includes a miniature fluid-cooled heatsink with integral heater and sensing elements. The device may be usedas part of a temperature control system to provide a controlledtemperature surface to an electronic DUT, such as a semiconductordevice, during the testing phase. In accordance with one exampleembodiment, the liquid-cooled heat sink includes two internal coolingpassages with inlets, outlets and heat transfer portions. The heattransfer portions are located on separate planes and may include coolingfins. There are two integral heaters positioned in the device. Differentembodiments are shown for the integral heater locations. In accordancewith another example embodiment, a temperature control device includes afluid-cooled heat sink structure configured to maintain a cross-flow ofcoolant in three-dimensions for the cooling of a DUT interface surface.The heat sink structure may employ a three-dimensional microchannelstructure that directs coolant flow in three dimensions within arespective fluid conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconjunction with the following Figures, wherein like reference numbersrefer to similar elements throughout the Figures.

FIG. 1 is an isometric view of a temperature control device forregulating the temperature of a device under test;

FIG. 2 is an exploded perspective view of the temperature control deviceof FIG. 1, showing the cooling layers and passages;

FIGS. 3-5 are exploded perspective views of various temperature controldevices, showing the heater layer positions in relation to the coolinglayers;

FIG. 6 is a perspective view of a temperature control device, showingthe DUT interface surface side;

FIG. 7 is a perspective view of the temperature control device shown inFIG. 6, showing the fluid entry/exit side;

FIG. 8 is an exploded perspective view of the temperature control deviceshown in FIGS. 6 and 7;

FIG. 9 is a top view of one of the outer layers of the temperaturecontrol device shown in FIG. 8;

FIG. 10 is a top view of one of the internal layers of the temperaturecontrol device shown in FIG. 8; and

FIG. 11 is a schematic perspective view of an example microchannelstructure that may be formed within the temperature control device shownin FIGS. 6 and 7.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A temperature control device configured in accordance with the inventionemploys a fluid-cooled heat sink structure that maintains a cross-flowof coolant in three dimensions for cooling a DUT interface surface ofthe temperature control device. In one example embodiment, the heat sinkstructure includes at least two layered heat transfer portions thatestablish the three-dimensional coolant flow. In another exampleembodiment, the heat sink structure includes a microchannel structurethat forces the coolant to flow in three dimensions within a fluidconduit or channel. Other practical embodiments may also fall within thescope and spirit of the invention.

A miniature fluid-cooled heat sink with integral heater and sensingelements is used as part of a temperature control system to provide acontrolled temperature surface to an electronic device, such as asemiconductor device, during the testing phase. The semiconductor deviceis placed either directly in contact with the device or with aninterface material or area-adapting heat spreader, such as a metalplate, while in use. In use, the integral heating element is used toheat itself and the device to a set temperature, the sensing elementsdetect the temperature, and the coolant flowing through the heat sinkremoves excess heat from the device.

A practical temperature control device can be designed to accommodatetest temperatures between −55 and 155 degrees Celsius. However, mostelectronic devices are typically tested at temperatures between −45 and120 degrees Celsius (these example temperature ranges may change in thefuture and the invention disclosed is not limited to any specific rangeof test temperatures). In addition, electronic device testspecifications do not usually call for temperature transients, i.e.,most electronic testing is performed at a substantially steady stateoperating temperature. One advantage of the devices described herein isthat their compact size, low thermal mass, and electronic heating allowvery rapid corrections to deviations from the setpoint temperature.Furthermore, the integral nature of the temperature control devicessimplifies the design and requires no subsequent assembly. Onceassembled, the monolithic nature of the devices, which use thermallyconductive materials, ensures that the fluid channel will effectivelyand repeatably remove heat.

FIG. 1 is a perspective view of one embodiment of a temperature controldevice 100 used for regulating the temperature of a DUT 102. Forpurposes of the example embodiment described herein, DUT 102 is anelectronic semiconductor circuit device, such as a microprocessor chip.Alternatively, DUT 102 may be any electronic, mechanical, or otherdevice being subjected to one or more tests performed under specifictemperature settings. The temperature control device 100 may cooperatewith a suitable testing system (not shown) that provides a power supply,coolant flow control, input signals, and possibly other inputs to DUT102. A typical testing system also monitors a number of outputs andsignals generated by DUT 102 during the test procedure.

The temperature control device 100 is designed to provide a controlledtemperature at an interface surface or first side 103 that provides athermal path from the temperature control device 100 to the DUT 102. TheDUT 102 is preferably held against or in close proximity to interfacesurface 103 of the temperature control device 100. Inside thetemperature control device 100 are internal cooling passages, integralheaters, and sensing elements. To regulate the temperature at theinterface surface 103, the integral heaters are turned on to provideheat and a fluid is directed through the cooling passages to providecooling. The subsequent figures and text will describe the coolingpassages and integral heater layers and their locations.

The temperature control device 100 may be regulated by a suitablyconfigured control system 101. The sensing elements are used to provideinput to the control system to monitor the temperature of thetemperature control device 100 and determine when it should be heated orcooled. The control system 101 generates a control signal that serves asan input signal to the integral heater and/or cooling system containedin temperature control device 100. The control signal may be generatedby control system 101 in response to one or more testing criteria,operating conditions, or feedback signals. For example, control system101 may generate a control signal in response to any of the followingparameters: a test temperature setting associated with the currenttesting specification for DUT 102; an input signal utilized by DUT 102,e.g., an input power signal, an input voltage, or an input current; asignal indicative of the real-time operating temperature of DUT 102; asignal indicative of the real-time operating temperature of an internalcomponent of DUT 102, e.g., a semiconductor die; a signal indicative ofthe real-time temperature of a portion of temperature control device100; the RF signature of DUT 102; or the like.

To cool the temperature control device 100, a fluid is passed through afirst internal cooling passage 104 and a second internal cooling passage106 (see FIG. 2). The fluid may be water, air, a refrigerant, or anyfluid substance having the desired thermal properties. The firstinternal cooling passage 104 has an inlet 108 and an outlet 109. Thesecond internal cooling passage 106 has an inlet 110 and an outlet 111.As shown in FIG. 1, a first fluid 112A enters through the first inlet108 and the fluid 112B exits through the first outlet 109. The secondfluid 114A enters through the second inlet 110 and the second fluid 114Bexits through the second outlet 111. The fluid travels through theinternal passages 104 and 106, cooling the temperature control device100. A coolant system (not shown) may provide the fluid 112 and 114 andcooperate with temperature control device 100 to regulate thetemperature and flow rate of the fluid. The coolant system pumps thefluid into temperature control device 100 through the inlets 108 and110, and receives the return fluid from the outlets 109 and 111. Theinlet and outlet ports may be designed with internal threads such thatsuitable fluid fittings (not shown) can be attached. The fluid fittingsreceive fluid delivery hoses or conduits that carry the fluid betweenthe temperature control device 100 and coolant system.

FIG. 2 is an exploded view showing some of the layers of the coolingportion of the temperature control device 100. The cooling portionincludes two cooling passages 104 and 106 that go through thetemperature control device 100. Each cooling passage has an inlet, anoutlet, and a heat transfer portion or layer that create a continuousfluid conduit through the device. The inlets and outlets are positionedin the cover layer 116, which may include one or more layers dependingon the design. The cover layer 116 shown in FIG. 2 has multiple layers116A, 116B and 116C that provide channels and passages to direct thefluid flow to the other layers and keep each of the fluid passagesseparate. The flow of the fluid paths through the cooling passages 104and 106 are shown in FIG. 2.

The first cooling passage 104 starts at the first inlet 108, in coverlayer 116A, opening to a passage on layer 116B that leads to a fluidopening 118A at a first end of the layer 116B. There may be subsequentfluid openings 118, depending on the number of layers and the positionof the first heat transfer portion or layer. In the figure shown, thereis a fluid opening 118B in layer 116C and a fluid opening 118C in layer120 that leads to a first heat transfer portion or layer 122. The firstheat transfer portion or layer 122 is designed such that fluid entersnear a first end, travels across the layer, through various openings orpassages, to a second end, where it exits the layer 122. To assist thefluid in spreading out in the heat transfer layer 122, there may be aplurality of fluid channels or fins 123 that lead from the first end tothe second end. The particular design of the fluid channels or fins 123may depend on any number of parameters, such as the thermal propertiesof the material, the thermal and physical properties of the fluid, theflow rate of the fluid, the size device, and the like. At the second endof the heat transfer layer 122, the fluid passage continues to a fluidopening 119C in layer 120, a fluid opening 119B in layer 116C, to afluid opening 119A in layer 116B, which finally leads to the firstoutlet 109.

The second cooling passage 106 starts at the second inlet 110 in coverlayer 116A, opening to a passage 124 through a layer 116B that leads toa passage in layer 116C that leads to a fluid opening 126, near fluidopening 199B in layer 116C. There may be subsequent fluid openings 126,depending on the number of layers and the position of the first heattransfer portion or layer. In the figure shown, the fluid opening 126leads to a second heat transfer portion or layer 120. The second heattransfer portion or layer 120 is designed such that fluid enters near afirst end, travels across the layer, through various openings orpassages to a second end, where it exits the layer 120. To assist thefluid in spreading out in the heat transfer layer 120, there may be aplurality of fluid channels or fins 121 that lead from the first end tothe second. The particular design of the fluid channels or fins 121 maydepend on any number of parameters such as the thermal properties of thematerial, the thermal and physical properties of the fluid, the flowrate of the fluid, the size device, and the like. At the second end ofthe heat transfer layer 120, the fluid passage 106 leads a to fluidopening 128 in layer 116C, to a fluid opening 130 in layer 116B, whichleads to the second outlet 111. The fluid can flow in either directionin the cooling passages, but for enhanced performance, the fluid shouldflow in opposite directions in each passage. One goal of this design isto reduce the surface temperature gradient of the temperature controldevice 100.

In the example embodiment, the first heat transfer portion 122 residesin a first plane and the second heat transfer portion 120 resides in asecond plane, where the first plane is closer to the interface surface103 than the second plane. In practice, the two planes are parallel toeach other, as depicted in FIG. 2. This stacked arrangement facilitatesa cross-flow of coolant in three dimensions. Although two heat transferlayers are shown in the figures, a practical implementation may employany number of heat transfer layers, whether directly stacked upon eachother or separated by one or more other elements.

There are two integral heaters used in the temperature control device100 shown, a first heater layer 132 and a second heater layer 134. Inpractice, any number of heater layers can be utilized. FIGS. 3-5 showexamples of some positions where the integral heater layers may belocated within the temperature control device 100. In these figures, thecover layer 116 is shown as a single layer, but may have multiplelayers, as described above. The heater layers 132 and 134 may be made ofelectrically resistive serpentine traces 138 on a substrate havingexternal connections 136 connected to a controller 101. The substratemay be made from silicon, ceramic or other appropriate material. Theresistive traces 138 may provide uniform heating or may be arranged toprovide differential heating with differential control. Whereappropriate, there may be fluid openings for fluid passages 104 and 106in the heater layers. In FIG. 3, the heater layers 132 and 134 are shownproximate the interface surface 103, such that the heat transfer layers120 and 122 are positioned between the heater layers 132 and 134 and thecover layer 116. Since the heater layers 132 and 134 are positioned awayfrom the cover layer 116 and heat transfer layers 120 and 122, there areno fluid openings required through the heater layers. In FIG. 4, theheat transfer layers 120 and 122 are proximate the interface surface 103and the heater layers 132 and 134 are positioned between the heattransfer layers 120 and 122 and the cover layer 116. Since the heaterlayers 132 and 134 are positioned between the cover layer 116 and theheat transfer layers 120 and 122, there are fluid openings 118 and 128through the heater layers 132 and 134 near a first end, and fluidopenings 119 and 126 through them near a second end as part of the fluidpassages 104 and 106. The electrically resistive serpentine traces 138are positioned on each heater layer 132 and 134 between the fluidopenings. In FIG. 5, the heater layer 132 is proximate the interfacesurface 103 and the heater layer 134 is proximate the cover layer 116.The heat transfer layers 120 and 122 are positioned between the heaterlayers 132 and 134. Since the heater layer 134 is positioned between thecover layer 116 and the heat transfer layers 120 and 122, there arefluid openings 118 and 128 through the heater layer 134 near a firstend, and fluid openings 119 and 126 through it near a second end as partof the fluid passages 104 and 106. The electrically resistive serpentinetrace 138 is positioned on the heater layer 134 between the fluidopenings.

One or more sensing elements are included in the temperature controldevice 100. The sensing elements are connected to the control system orother means of monitoring the sensor readings. The sensing elements maybe used to indicate the temperatures at one or more locations in thetemperature control device 100. For example, the sensors may monitor theinterface surface 103 temperature, the heater layer 132 and 134temperatures (separately or combined), the fluid temperatures or heattransfer layer temperature (separately or combined) and other placeswhere sensing may be appropriate or desired.

In operation, temperature control device 100 may thermally condition theDUT 102 by providing a controlled thermal surface 103 to the DUT 102during a testing phase. The DUT 102 is placed either directly in contactwith the device or uses an interface material or area-adapting heatspreader, such as a metal plate, while in use. The DUT 102 is thensubjected to the functional testing as required by the testspecification. The control system 101, or test equipment, monitors thetemperature of DUT 102 during the functional test and regulates thetemperature of the heating and cooling elements associated withtemperature control device 100. The integral heater layers 132 and 134may be turned on and off, either together or separately, with varyingpower levels, to heat the device, and cooling fluid flows through thefluid passages 104 and 106 to cool the device. In one practicalembodiment, the temperature of each heating element is independentlycontrolled by adjusting the respective power applied to the element.

The temperature control device 100 is configured to heat or cool the DUTby providing a direct thermal path to the DUT. In accordance theembodiments shown, the thermal path to the DUT is from the controlledthermal interface surface 103 to the cover layer(s) 116. In FIG. 3, thethermal path includes the first heater layer 132, the second heaterlayer 134, the first heat transfer layer 122 and the second heattransfer layer 120. In FIG. 4, the thermal path includes the first heattransfer layer 122, the second heat transfer layer 120 the first heaterlayer 132 and the second heater layer 134,. In FIG. 5, the thermal pathincludes the first heater layer 132, first heat transfer layer 122, thesecond heat transfer layer 120 and the second heater layer 134. Theremay additional configurations that provide additional thermal paths.

Of course, the size and shape of the controlled thermal interfacesurface 103 of the temperature control device 100 may be suitablyconfigured to mate with the size and shape of the particular DUT. Forexample, to test a common microprocessor, the size of the device may be1 inch wide by 2 inches long and 0.25 inches thick (other sizes andshapes can be employed to accommodate the particular application).Alternatively, a suitably configured mating element, formed from athermal conductor, can be placed between temperature control device 100and the DUT 102. A mating element may be desirable to accommodate thespecific physical characteristics of the DUT or to concentrate heatingor cooling in certain areas of the DUT.

As mentioned above, the heat transfer layers 120 and 122 may include anumber of cooling fins that are configured and arranged to promote heattransfer from to the fluid or coolant. The plurality of parallel coolingfins are also parallel to the fluid flow path in the heat transferlayers 120 and 122. In accordance with a practical embodiment, each ofthe cooling fins is approximately 0.012 inches thick. Furthermore,neighboring cooling fins are separated by approximately 0.012 inches.Alternatively, the heat transfer layers may employ any suitable coolingfin design and the particular design may depend on any number ofparameters such as the thermal properties of the heat sink material, thethermal and physical properties of the coolant, the flow rate of thecoolant, the size of heat transfer layers, and the like.

Electrically conductive “ink” may be used to form the electricallyresistive serpentine traces 138 on the substrate. In accordance with onepractical embodiment, the conductive ink includes a nickel, tungsten, orother alloy having a relatively high electrical resistance. Thesubstrate is patterned and the conductive ink is printed onto thesurface of the substrate, which might then be joined to additionallayers by stacking. Signal wires or leads 136 are soldered or otherwiseattached to the respective traces to carry the respective heater controlsignals from the control system. The electrical heating elements tracesare not exposed to the DUT.

Numerous methods of manufacture may be used to construct the temperaturecontrol device 100. In one embodiment, all of the layer substrates aremanufactured in a “green” ceramic state, then once the fluid channels,electrically resistive metallic serpentine traces, sensors andconnections have been formed on the substrates, the layers are joined byco-firing forming a monolithic type structure. In another embodiment,the layer substrates are silicon and once the fluid channels,electrically resistive metallic serpentine traces, sensors andconnections have been formed on the substrates, the layers are joined byeutectic bonding, or other high-thermal-conductivity joining process.

FIGS. 6-11 show various views of another temperature control device 200configured in accordance with the invention. Like the temperaturecontrol device described above, the device 200 generally includes aninterface surface 202 configured to provide a thermal path to a DUT, afluid-cooled heat sink structure 204 configured to maintain a cross-flowof coolant in three dimensions for cooling interface surface 202; and aheater assembly 206 configured to heat interface surface 202.

Heater assembly 206 may be configured as described above in connectionwith device 100. Heater assembly 206 includes one or more electricalheater elements coupled to a substrate. As shown in FIG. 8, heaterassembly 206 may include a number of terminals or contact points (hiddenfrom view) that accommodate one or more heater control signals. In atypical implementation, the control signals are fed through holes in theheat sink en route to the terminals on heater assembly 206. Inoperation, interface surface 202 is held against a DUT (not shown),heater assembly 206 is controlled to regulate heat applied to the DUT,and coolant is passed through heat sink structure 204 to regulate thetemperature of the DUT. The flow rate and/or temperature of the coolantcan be controlled by a coolant flow control system (not shown) coupledto the device 200. In this regard, device 200 includes one or more fluidinlets 210 and one or more fluid outlets 212 formed therein toaccommodate the flow of coolant. For clarity, fluid coupling elementsfor the inlets 210 and outlets 212 are not shown in connection withdevice 200.

Temperature control device 200 is preferably formed from a plurality oflayers, as best shown in FIG. 8. The illustrated embodiment includesheater assembly 206, a first cover layer 214, a first intermediate layer216, a plurality of microchannel layers 218, a second intermediate layer220 having fluid inlets and fluid outlets formed therein, and a secondcover layer 222 having fluid inlets and fluid outlets formed therein.The various layers are coupled together using one or more knowntechniques such as bonding, soldering, adhesive, or the like. After thestack is constructed, the fluid inlets and outlets formed in secondintermediate layer 220 and second cover layer 222 form fluid inlets 210and fluid outlets 212.

In a practical embodiment of temperature control device 200, first coverlayer 214 is formed from copper, first intermediate layer 216 is formedfrom a ceramic substrate material, each of the microchannel layers 218is formed from copper, second intermediate layer 220 is formed from aceramic substrate material, and second cover layer 222 is formed fromcopper. First and second intermediate layers 216 and 220 function to“isolate” the effects of thermal expansion and contraction of the copperlayers from heater assembly 206 (which, in the example embodiment, isceramic based). The layers are coupled together in a manner that formsfluid seals such that the cooling fluid is maintained in the properchannels and flow paths within heat sink structure 204. In other words,heat sink structure 204 is formed such that (ideally) the cooling fluidcan only enter through fluid inlets 210 and only exit through fluidoutlets 212.

Referring to FIG. 10, each of the microchannel layers 218 includes ribs224 that separate adjacent fluid conduits 226 from one another. Themicrochannel layer 218 shown in FIG. 10 includes seven ribs 224 andeight conduits 226. After the various microchannel layers 218 arestacked together, ribs 224 form “walls” between adjacent conduits 226.In accordance with one practical embodiment, ribs 224 are eachapproximately 0.020 inches wide, each conduit 226 is approximately 1.850inches long, and (after stacking) heat sink structure is approximately0.158 inches thick. Of course, these dimensions can vary to accommodatedifferent applications and different DUT sizes.

Temperature control device 200 is suitably configured to establish across-flow of coolant within heat sink structure 204. In the exampleembodiment, fluid conduits 226 are coplanar and parallel. In addition,one subset of the fluid conduits 226 accommodate coolant flow in a firstdirection while another subset of the fluid conduits 226 accommodatecoolant flow in a second direction. Preferably, the first direction isopposite to the second direction. Referring to FIG. 9, device 200maintains the coolant cross-flow by directing the coolant into certainfluid inlets 210. In this regard, fluid inlets 210 a-d, whichrespectively correspond to fluid outlets 212 a-d, accommodate coolantflow in a first direction (from the top to the bottom of FIG. 9). Incontrast, fluid inlets 210 e-h, which respectively correspond to fluidoutlets 212 e-h, accommodate coolant flow in a second direction (fromthe bottom to the top of FIG. 9). This flow pattern results in adifferent flow direction in adjacent conduits 226. Ultimately, thecoolant cross-flow reduces the thermal gradient over the interfacesurface 206 and results in more efficient temperature regulation of theDUT.

Each microchannel layer 218 also includes a web, mesh, matrix, lattice,or similar structure 228 located within the fluid conduits 226. The webstructure 228 may employ a geometric pattern, e.g., squares, triangles,circles, hexagons, octagons, or the like. As shown in FIG. 11, theexample embodiment employs a lattice of hexagons for web structure 228.In the illustrated embodiment, the web structure 228 in eachmicrochannel layer 218 is planar or flat such that only one “level” ofhexagons reside in each microchannel layer 218. The web structure 228 inadjacent stacked microchannel layers 218 is staggered or offset suchthat, when heat sink structure 204 is formed, the web structures 228create respective three-dimensional microchannel structures locatedwithin the various fluid conduits 226. FIG. 11 depicts three offset webstructures 228 forming such a three-dimensional microchannel structure.

The resulting three-dimensional microchannel structures are configuredto direct coolant flow in three dimensions within each fluid conduit.Due to the offset nature of the individual web structures 228, thecoolant will flow laterally through the three-dimensional microchannelstructure while flowing vertically over and under the individual webstructure levels. The individual web structures 228 may be arranged andcoupled together such that continuous heat transfer paths are formedfrom the top to the bottom of heat sink structure 204, thus improvingthe heat transfer efficiency.

In the example embodiment shown herein, fluid conduits 226 andrespective microchannel structures are adjacent to one another. In analternate embodiment (not shown), a first subset of fluid conduits arelocated at one layer, a second subset of fluid conduits are located at asecond layer below the first layer, and both groups of fluid conduitsare located above interface surface 206. Coolant cross-flow may beestablished in the manner described above and/or by directing coolant inone direction through the first subset of fluid conduits and in a seconddirection through the second subset of fluid conduits.

The layered design of these devices allows the flexibility to tailor theheat sink efficiency and the pressure drop across the heat sink bysimply changing the number of layers. In this regard, more layersresults in higher heat sink efficiency to remove heat, which in turnresults in a better response time for an active thermal control system.Additional layers also results in lower pressure drop as the coolingfluid flows across the heat sink. Lower pressure drop results in a lowercooling fluid inlet pressure requirement, which is desirable forpractical applications. Additional layers also results in higher thermalmass for the heat sink. Consequently, the layered heat sink designfacilitates rapid cost effective provisioning of an optimized device forthe given application by allowing the designer to strike a balancebetween thermal efficiency and thermal mass.

The present invention has been described above with reference topreferred embodiments. However, those skilled in the art having readthis disclosure will recognize that changes and modifications may bemade to the preferred embodiment without departing from the scope of thepresent invention. These and other changes or modifications are intendedto be included within the scope of the present invention, as expressedin the following claims.

1. A temperature control device comprising: an interface surfaceconfigured to provide a thermal path to a device under test (“DUT”); afluid-cooled heat sink having a first heat transfer portion in a firstplane and a second heat transfer portion in a second plane, said firstplane being closer to said interface surface than said second plane; andone or more integral heater assemblies.
 2. A temperature control deviceaccording to claim 1, further comprising one or more thermal sensingelements.
 3. A temperature control device according to claim 1, whereinsaid first heat transfer portion includes one or more flow channels andsaid second heat transfer portion includes one or more flow channels. 4.A temperature control device according to claim 1, wherein said firstheat transfer portion has a flow path in a first direction and saidsecond heat transfer portion has a flow path in a second direction.
 5. Atemperature control device according to claim 4, wherein said flow pathin said first direction is opposite to said flow path in said seconddirection.
 6. A temperature control device according to claim 1, whereinsaid one or more integral heater assemblies are planar and parallel tosaid interface surface.
 7. A temperature control device according toclaim 1, wherein said one or more integral heater assemblies includes asubstrate and at least one heating element formed on said substrate. 8.A temperature control device according to claim 7, wherein said at leastone heating element comprises one or more electrically resistiveserpentine traces.
 9. A temperature control device according to claim 1,wherein each of said one or more integral heater assemblies has anindependently adjustable power level.
 10. A temperature control devicecomprising: an interface surface configured to provide a thermal path toa device under test (“DUT”); a fluid-cooled heat sink structureconfigured to maintain a cross-flow of coolant in three dimensions forcooling said interface surface; and a heater assembly configured to heatsaid interface surface.
 11. A temperature control device according toclaim 10, wherein said fluid-cooled heat sink structure comprises: afirst fluid conduit for accommodating coolant flow in a first direction;a first three-dimensional microchannel structure located within saidfirst fluid conduit, said first microchannel structure being configuredto direct coolant flow in three dimensions within said first fluidconduit; a second fluid conduit for accommodating coolant flow in asecond direction different than said first direction; and a secondthree-dimensional microchannel structure located within said secondfluid conduit, said second microchannel structure being configured todirect coolant flow in three dimensions within said second fluidconduit.
 12. A temperature control device according to claim 11, whereinsaid first and second fluid conduits are coplanar.
 13. A temperaturecontrol device according to claim 12, wherein said first and secondfluid conduits are adjacent to each other.
 14. A temperature controldevice according to claim 11, wherein: said first fluid conduit islocated above said second fluid conduit; and said first and second fluidconduits are located above said interface surface.
 15. A temperaturecontrol device according to claim 10, wherein said heater assembly islocated between said interface surface and said fluid-cooled heat sinkstructure.
 16. A temperature control device according to claim 10,wherein said fluid-cooled heat sink structure comprises: a first layer;a second layer below said first layer; a first plurality of flowchannels, formed in said first layer, for accommodating coolant flowwithin said fluid-cooled heat sink structure; and a second plurality offlow channels, formed in said second layer, for accommodating coolantflow within said fluid-cooled heat sink structure.
 17. A temperaturecontrol device according to claim 16, wherein said first and secondlayers are parallel to each other.
 18. A temperature control deviceaccording to claim 16, wherein: said first plurality of flow channelsare configured to maintain a first flow path having a first direction;and said second plurality of flow channels are configured to maintain asecond flow path having a second direction different than said firstdirection.
 19. A temperature control device according to claim 18,wherein said first flow path is opposite to said second flow path.
 20. Atemperature control device comprising: an interface surface configuredto provide a thermal path to a device under test (“DUT”); and afluid-cooled heat sink structure configured to maintain a cross-flow ofcoolant in three-dimensions for cooling said interface surface, saidfluid-cooled heat sink structure comprising: a first fluid conduit foraccommodating coolant flow in a first direction; a firstthree-dimensional microchannel structure located within said first fluidconduit, said first microchannel structure being configured to directcoolant flow in three dimensions within said first fluid conduit; asecond fluid conduit for accommodating coolant flow in a seconddirection different than said first direction; and a secondthree-dimensional microchannel structure located within said secondfluid conduit, said second microchannel structure being configured todirect coolant flow in three dimensions within said second fluidconduit.
 21. A temperature control device according to claim 20, furthercomprising a heater assembly configured to heat said interface surface.22. A temperature control device according to claim 20, wherein saidfirst and second fluid conduits are coplanar.
 23. A temperature controldevice according to claim 20, wherein: said first fluid conduit islocated above said second fluid conduit; and said first and second fluidconduits are located above said interface surface.